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June 29 1926.

C. BOL ET AL ELECTRIC DISCHARGE TUBE Filed June 27, 1924 Patented June 29, 1926.

UNITED STATES PATENT orFics.

CORNELIS BOL AND BALTHASAB VAN DIR POL, OF E INDHOVEN, NET I SIGNOBS TO N. V. PHILIPS GLOEIIFLAIPENIAIBRIEKEN, OII nmnnovnnn'rnm LANDS.

nmicrmc mscnancn TUBE.

Application filed June 27, 1924, Serial No. 728,793, and in, Netherlands July 18, um.

This invention has reference to electric discharge tubes having an incandescent cath- Ode, an anode adapted to be cooled and one or more controlling electrodes, and more particularly to discharge tubes of this kind of high power as used for example in transmission stations for wireless telegraphy or telephony.

Discharge tubes of this kind in which the 1, cooled anode may form art of .the outer envelope of the tube can e constructed up to much greater power than discharge tubes the anode of which is not cooled and the maximum of the power of such tubes is no longer determined by the heating of the anode but by that of the controlling electrodes (grids) caused by the high positive value which the 'id potential may attain during the operation of the tube. To avoid overheating of the controlling electrodes, discharge tubes of the kinddescribed are, according to the invention, char acterized by one or more metal vessels form-- .fing part of the outer envelope of the tube and serving partly or wholly as controlligg electrodes. Such electrodes may be cool for example, by circulating water, or by radiation.

If the discharge tube is T irovidedvvith an. f t e outer envelope 0 anode that forms part 0 of the tube, aseoond metal vessel ma be arranged within the said anode and likewise form part of the outer envelo of the tube said vessel serving partly or w olly as a 5 electrode. It must be mentioned that the outer envelope of the tube? is to be understood to mean the wall separating the vacuum of the tube from the atmosphere. If the anode and the metal vessel serving partly 4. or wholly as a grid electrode are arranged concentrically and cylindrically, the incan descent cathode may consist of a number of wires, stretched parallel to the axis of the M other electrodes.

In this construction the metal vessel arranged within .the anode may be provided with longitudinal coves and a grid wire be wound'on the IlbS between the grooves, the incandescent cathode consisting of a number of wires extending in the longitudinalgrooves between the metal vessel and the grid wire. The grid wire may e Omitted .ferent form of execution hav so that the incandescent cathode lies between the grid electrode and the anode. In this construction the grooves in the metal vessel which serves as a grid electrode, are preferably so shaped and the wires of the incan descent cathode so arranged in relation thereto that the distribution of the fieldat the surface of the wires is practically uniform.

Various other new'characteristics of discharge tubes according to the invention will be apparent from the following description. The accompanying drawing represents some embodiments of. transmission triodes according to the invention; In 'the said drawing Figure 1 1s a vertical section of a three electrode transmission triode having the grid arranged between the incandescent Wire and the anode.-

Figure 2 is a horizontal section on a large .scalel taken along the line IIII of Figure Fi re 3 is a horizontal section taken on the hue III-III of Figure 1.

Figure 4 is a horizontal section ofa dif- 'the incandescent wire arranged between e grid and the anode. Y

f F re- 5 is a perspective view .of a device wire.

ing'the lower end of the incandescent The transmission triode according to the invention comprises a metal anode 1 forming part of theouter envelope of the discharge tube. The end of the vessel 1 is hermetically sealed to a las sealing member 2. The ves- S01 1 is furt ermore threaded so as to enable the anode of being located in a cooling vessel 3, partly shown in the drawing. The anode may consequently'be cooled from the outside by any suitable cooling-means, for example by water enclosed within the vessel 3.

The vessel 2- has hermetically fused to it glass .'tubes 4 and 5 extending inwardly and also a centrally arranged tube 6. The latter has fused-to its end a; hollow metal vessel 7 carrying the grid wire. At the mt'of .fusin 8, the thickness'of ,the w; of the tube is preferably slightly thinner so as to facilitate the fusing operation. The same remark applies to the oint' of fusing 9 of the vessel 1. The vesse land. 7 may cent wires from with the vessel 7 and the any suitable metallic material which is read-* ily hermetically sealed to glass and 1s nonporous. In practice chrome iron of such composition that its coefficient of expansion corresponds to that of the glass gives excellent results.

The vessel 7 may be cooled from the inside by any, suitable cooling means. A supply tube 12 and a discharge tube 13 put into the upper end of the tube 6 by means of a stopper 14, for example, of rubber serve for this purpose. The vessel 7 is provided with a number of ribs 10 and the grid wire 11 is helically wound on thesaid ribs (Figure 3). For the sake of clearness the grid wire is not shewn in Figure 1. In order to facilitate the attachment of the grid-wire, grooves may be cut in the ribs 10.

For the hermetical introduction of the leading-in wires for the incandescent cathode, metal caps 16' and 17 are hermetically fused to the ends of the tubes 4 and 5.

These caps may consist of material whlchis readily-hermetically fused to glass, such for example as platinum. Very good results are also obtainedby chrome iron of such composition that its coeiiicient of expansion corresponds to that of the glass.

On both sides of the cap 16 and 17 are fixed rods 18, 19 and 20, 21 respectively, which,'if the caps are of chrome iron, are preferably of material that is readily welded to chrome iron, for'example nickel. To the rods 18 and 20 are fixed leading-in wires 22 and 23, for example of copper, and to the ends of the rods 19 and 21 areconnected leading-in wires 24 and 25, which preferably consist of highly refractory material, such for example as molybdenum.

The incandescent cathode consists of three wires 26, 27 and 28, forexample of tungsten, mounted in parallel and shaped as'a U with a deep indentation. Current is supplied to these wires not only :by the aforesaid wires 24 and 25 but also by bent lead- 1ng-in wiresl29 and 30 which by welding, soldering, or inany other suitable manner are attached in grooves in the rods 19 and '21. The parallel legs of the incandescent wires lie in the grooves between the ribs 10, between the wall of the vessel 7 and the grid wire 11.

The three wires are at their lower ends fixed by small helixes 32 to a mug 33, to-

gether with clips 34 (Figure 5). are fixed to a plate 35 carrying The clips small rods 36 and These rods are capable of mov ing vertlcally in quartz tubes 38 and 39 mounted at thev bottom of the vessel 7 by means of a small cover 40.

This construction prevents the incandesdistorting and contacting grid wire 11, when expanding'by heat.

F shows a cross-section of a diiferent become positive or ea ers tion of the discharge tube may otherwise correspond to that shown in Figures 1, 2 and 3. As a rule the amplification factor in the arrangement shown in Figure 4 will be low, for example lower than 10.

In this construction the vessel 7 serving as a grid could be simply cylindrical without ribs, butthis 'resul s in an unequal distribution of the field at the surface of the incandescent wire which may cause difliculties. For this reason the ribs 10 may be disposed as shown in Figure 4 so that the distribution of the field at the surface of the filament becomes more uniform.

If the amplification factor in an arrange- Jnent as shown in Figure 4 isloW, this has the additional advantage that it is possible, without increasing the anode tension to an abnormally high extent, to choose such a negative grid tension that the grid does not at least only to a negligible extent when oscillating during the o eration of the tube so that also the grid absorbs practically no energy.

Yet it may be desirable in such a construction having a low amplification factor to cool the grid, because in discharge tubes of very high power especially in an arrangement as shown in Figure 4, the grid may be heated to a very high extent by the heat radiation of the incandescent cathode and it is also important that the energy absorbed by the grid may be conducted away, 7

when the grid-tension unexpectedly reaches positive values relative to the'incandescent wire.

It must be mentioned'that the amplification factor 9 is to be understood to mean the partial differential coefiicient of the anode tension to the grid tension the anode current being kept constant pi t g- 5V9 ze-cons oscillation circuit in series with the selfinduction, the capacity (G) in the oscillation circuit and the resistance (r) of the discharge tube have such a value that as this is the condition for oscillating. In this. circuit arrangement it is very important that the grid obtains a sufficiently high negative potential, as there is a phase difference of 180 between the grid tension and the anode tension and consequently the lowest anode tension just corresponds to the highest grid tension, which'of course assists to form grid currents. If g is low enough it will always be possible to find at the normal anode tension a id tension having such a high negative va ue that no grid currents or'hardly any occur during oscillation.

If a circuit arrangement Without retroaction is chosen and a forced oscillation is impressed on the grid, the energy in the anode circuit will decrease it is true by choosing velope of the tube serves as controlling electrode. a

2. A discharge tube having an incandescent cathode, an anode that forms part of the outer-envelope, and'at least one controlelectrode 0 aracterized in that within the anode is arranged a secondmetal vessel that likewiseforms art of the outer envelope of the tube an serves as a grid electrode. a

3. A discharge tube according .to claim 2, characterized in that the metal vessel ar- 1 within the anode and formin part of tde'outer envelope isdprovidfiedmvgit 10nd itu inal grooves a gri wire woun fin the ribs betwizen the groovesyand that the incandescent cathode consists of a number of wires extending in the longitudinal grooves between the metal vessel and the grid wire.

4. A discharge tube in which the anode and the metal vessel which, according to claim 2, serves as a grid electrode are arranged concentrically and cylindrically, characterized in that the incandescent cathode comprises a number of wires which are parallel to the axis of the other electrodes. 5. A discharge tube according to claim 2, characterized in that the metal vessel, which serves entirely as a grid electrode, is provided with longitudinal grooves, and the incandescent cathode comprisesa number of wires which are arranged in the said grooves, the grooves and wires "beingpreferably so shaped and. arranged that the distribution of the field on the surface of the wires is.

practically uniform.

6. A discharge tube according to claim 2,-

in which the electrodes are cylindrically and concentrically arranged, characterized in -that the anode has hermetically sealed to ita glass vessel provided with two inwardly ex tending tubes for the hermetical introduction of the leading-in wires -for the incandescent cathode, and with a central tube extending upwardly and having hermetically sealed to its end the second metal vessel.

7. A discharge tube according to claim 2, in which the metal vessel arranged within the anode andforming part of the outer envelope is provided with longitudinal grooves, a grid wire being wound on the ribs between said grooves, and a plurality of incandescent cathode wires extending in said grooves between the metal vessel and the grid wire,

characterized in that the incandescent wires extending between the anode and'the grid electrode are united at one-end by a ring provided with a number of clips which are so connected to the bottom of the metal vessel, from which they are insulated, that they can only move rectilinearly in the direction of the incandescent wire.

In testimon whereof we afiix our signatimes, at the city of Eindhoven, this 4th day 7,

of June 1924. v

' CORNELIS BOL.

BALTHASAR VAN on POL. 

